Seagate Personal Cloud is a consumer-grade Network-Attached Storage
device (NAS). By default Seagate Media Server allows unauthenticated
users to upload files to a public share. Once a file is uploaded it can
also be downloaded again from the NAS.

No restrictions are enforced on which file types a user can upload, any
type of file can be uploaded including executable files & HTML files.
File downloads are directly handled by Lighttpd and because of this file
are processed based on its (MIME) type. An attacker can upload an HTML
file and cause Lighttpd to treat the file as a regular web page.
Consequently, uploading an HTML file can be used to execute a stored
Cross-Site Scripting attack.